This application claims the benefit of Korean Application No. 2001-75676, filed Dec. 1, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method of determining a time to replace a developing solution using a color difference depending on the degree of contamination of the developing solution in a printer.
2. Description of the Related Art
A developing solution of a printer is a mixed solution of a toner and a carrier to dissolve the toner and provides a developing agent used to develop a latent electrostatic image.
FIG. 1 is a sectional view of a conventional wet color printer. Referring to FIG. 1, the wet color printer includes a photoreceptor belt 14, a charger 15 to charge the photoreceptor belt 14, laser scanning units 16 to scan light onto the charged photoreceptor belt 14 to form a latent electrostatic image, developers 30 to develop the latent electrostatic image, a drier 18 to absorb a liquid carrier on the photoreceptor belt 14 and to evaporate the liquid carrier, and a transfer unit 20 to transfer an image to a sheet 23.
The photoreceptor belt 14 is entrained about a plurality of rollers including a drive roller 11 and driven rollers 12 and 13. The sheet 23 is led into the transfer unit 20 by the rotation a transfer roller 21 and a fusing roller 22, and an image is transferred to the sheet 23. The laser scanning units 16 scan color information of yellow (Y), cyan (C), magenta (M), and black (K) onto the photoreceptor belt 14. The corresponding developers 30 supply developing solutions of corresponding colors to the photoreceptor belt 14. Each of the developers 30 includes a developing solution supplier 32 to supply a developing solution to the photoreceptor belt 14, and a developer tank 31 to collect the developing solution that drops from the photoreceptor belt 14. The developer tank 31 includes a developer roller 36, a brush roller 37 to remove the developing solution from the developer roller 36, a squeeze roller 34 to extract a liquid carrier which does not form an image from the developing solution supplied onto the photoreceptor belt 14, and a plate 35 to guide the carrier extracted through the squeeze roller 34 to the developer tank 31.
The developing solution supplier 32 is provided with a developing solution of an appropriate concentration. The developing solution is made by mixing a solvent (i.e., a liquid carrier (NORPAR)) and a developer (i.e., a toner) from a developing solution providing unit 38 and a developing solution from the developer tank 31, and supplies the developing solution to the photoreceptor belt 14.
In such a conventional wet electrophotographic color printer, a carrier dissolves a toner attached to the photoreceptor belt 14 to develop a latent electrostatic image during development. The carrier may not be collected into a developer tank 31 provided for a color corresponding to the carrier, but may be transported attached to the photoreceptor belt 14 to a developer tank 31 provided for other colors. In addition, when some of a toner is not transferred to the sheet 23 and remains on the photoreceptor belt 14 even after transferring performed by transfer unit 20, the toner may be collected into a developer tank 31 which does not correspond to the color of the toner while the photoreceptor belt 14 circulates. In this case, different colors are mixed within the developing solution suppliers 32, so an image of desired colors cannot be obtained and a picture quality deteriorates. Particularly, when a black toner is mixed with a yellow toner, it is very difficult to present a normal yellow color, which fatally affects the quality of printing.
To solve the above and other problems, it is an object of the present invention to provide a method of determining a time to replace a developing solution by simply measuring the degree of contamination of the developing solution.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects of the present invention, there is provided a method of determining a time to replace a developing solution in a wet electrophotographic printer including developing solutions of predetermined colors according to an embodiment of the invention, the method comprising providing a reference card in which sample patches of standard colors for the predetermined colors of the developing solutions, sample patches of test colors into which the standard colors change due to contamination, and standard color differences xcex94E* calculated from standard color values Es* corresponding to the respective standard colors and measured standard contamination values Ec* corresponding to the respective test colors are arranged; inputting information about test patches for the predetermined colors into the printer and printing the test patches; and comparing the sample patches with the test patches to determine whether to replace the developing solutions.
According to an aspect of the invention, the providing the reference card includes setting the standard colors for the predetermined colors and the test colors into which the standard colors change depending on contamination; calculating the standard color values Es* corresponding to the respective standard colors and the measured standard contamination values Ec* corresponding to the respective test colors; calculating the standard color differences xcex94E* from the standard color values Es* and the measured standard contamination values Ec*; and providing the reference card in which the sample patches corresponding to the standard colors and the sample patches corresponding to the test colors are arranged in order of the standard color differences xcex94E*.
According to another aspect of the invention, in the setting the standard colors, each of the standard color values Es* is defined by three variable values including a standard value of lightness Ls*, a standard value of red-greenness as*, and a standard value of yellow-blueness bs*, and each of the measured standard contamination values Ec* is defined by three variable values including a measured standard contamination value of lightness Lc*, a measured standard contamination value of red-greenness ac*, and a measured standard contamination value of yellow-blueness bc*.
According to yet another aspect of the invention, in the calculating the standard differences xcex94E*, the standard color differences xcex94E* satisfy Equation (1).
xcex94E*={(xcex94L*)2+(xcex94a*)2+(xcex94b*)2}1/2
xcex94L*=Ls*xe2x88x92Lc*
xcex94a*=as*xe2x88x92ac*
xcex94b*=bs*xe2x88x92bc*xe2x80x83xe2x80x83(1)
According to still another aspect of the invention, the inputting the information about the test patches includes inputting the information about the test patches into the printer; commanding the printer to print the test patches; and printing the test patches in response to the command.
According to a further aspect of the invention, in the printing the test patches, measured contamination values Ec of the respective test patches are printed together with the test patches.
According to a still further aspect of the invention, each of the measured contamination values Ec is defined by three variable values including a measured contamination value of lightness Lc, a measured contamination value of red-greenness ac, and a measured contamination value of yellow-blueness bc.
According to a yet further aspect of the invention, in the printing the test patches, measured color differences xcex94E corresponding to the measured contamination values Ec of the respective test patches are also printed together with the test patches.
According to a still yet further aspect of the invention, the measured color differences xcex94E satisfy Equation (2).
xcex94E={(xcex94L)2+(xcex94a)2+(xcex94b)2}1/2
xcex94L=Ls*xe2x88x92Lc
xcex94a=as*xe2x88x92ac
xcex94b=bs*xe2x88x92bcxe2x80x83xe2x80x83(2)
According to an additional aspect of the invention, the comparing the sample patches with the test patches includes comparing the sample patches with the test patches; and replacing a developing solution when it is determined that a test patch corresponding to the color of the developing solution is more contaminated than a sample patch corresponding to a particular measured standard contamination value Ec* for the color of the developing solution.
According to another embodiment of the present invention, a reference card includes standard colors for predetermined colors, test colors into which the standard colors change due to contamination, and color differences calculated from standard color values corresponding to the respective standard colors and measured standard contamination values corresponding to the respective test colors, the reference card to be provided with a printer including information about test patches for the predetermined colors so that users can easily discriminate the degrees of contamination of developing solutions with the naked eye and simply determine a time to replace each of the developing solutions.